1. Field of the Invention
The present invention relates generally to dispensers and, more particularly, to dispensers able to dispense more than one material from a divided cartridge.
2. Description of the Prior Art
Dispensers have been generally used for extruding material from a cartridge. The cartridge, in the present case, includes at least two chambers, each chamber containing a different type of material. The dispenser dispenses a predetermined amount of each material from the chambers and delivers the material to a static mixer. The materials will then be mixed together in the static mixer.
In general, dispensers are typically in the form of a pistol including a handle, a trigger and a body portion. A cartridge is loaded in the body portion of the dispenser and the trigger is pulled. The trigger exerts a force on a ratchet which is engaged with a plunger. The force exerted on the ratchet is in a direction towards the cartridge. The ratchet, due to its engagement with the plunger, exerts a force on the plunger which extends into the cartridge. This pushes the plunger deeper into the cartridge forcing material within the cartridge chambers out of the cartridge through outlets at a dispensing end of the cartridge. The material enters a static mixer connected at the dispensing end where it is then mixed and dispensed for use.
When the desired amount of material is dispensed, the material remaining needs to settle within the cartridge. Afterflow of the material is a problem encountered when the material is settling. This occurs when, upon settling, material exits the cartridge through the dispensing end. When this occurs, the material within the different chambers of the cartridge collects at the outside of the dispensing end of the cartridge. This may result in the materials mixing and hardening at the discharge end of the cartridge. The hardening of the material in this manner may restrict further use of the cartridge.
An example of a typical dispenser is shown in U.S. Pat. No. 4,826,053. This patent discloses separate components for activating the plunger and for pulling it back a short distance after activation. For activation, the trigger is pulled, releasing a ratchet arm from its position between two sawteeth on the ram. The ram is driven forward a distance and the ratchet arm comes to rest between the next two sawteeth behind its previous position. To provide the backward motion, when the ram is moved forward, it coils a spring attached between a stationary support part and a retrieval element attached around the ram. Once the forward motion ceases, the spring recoils moving the ram back a short distance.
U.S. Pat. No. 4,911,328 discloses another prior art dispenser which guides a pair of pistons evenly through the chambers of a cartridge while eliminating tilting of the pistons due to unequal forces. These unequal forces are a result of possibly different viscosities of the material within the chambers and/or different cross sections of the chambers. The pistons are engaged by a plunger when inserted into a dispenser.
U.S. Pat. No. 4,834,268 discloses another prior art dispenser having a piston with an annular sealing means and rigid head with a first grooved portion in the piston head and a second grooved portion in the piston wall. When thrust is applied to the piston, the grooved portions deform, squeezing the sealing means from the grooves and thereafter releasing the sealing means upon stopping the thrust allowing the piston to move in the opposite direction.
While some of the prior art dispensers have been designed to prevent the afterflow of the material, they have not proven to be very effective. Also these prior art devices have not had other safety features needed for a dispenser.
It is therefore desired to have a dispenser which does not allow dispensing of material when the cartridge is not secured in place, which provides a backward motion of the plunger to prevent afterflow of the material, and a device which would also prevent sliding of the plunger when the plunger is not under control of the ratchet.